The United Nations Support Mission in Libya (UNSMIL) on Sunday expressed concern over reports of excessive use of force against demonstrators in the eastern Libyan city of al-Marj.

"UNSMIL expresses grave concern regarding reports that one civilian was killed, three were injured, and a number of other demonstrators were arrested on 12 September following the reported excessive use of force by eastern authorities against peaceful demonstrators in the city of al-Marj," the UNSMIL said in a statement.

The UNSMIL called for a thorough and immediate investigation into these incidents and for the speedy release of all those arbitrarily arrested and detained.

"The UNSMIL reminds all parties in Libya that the rights to peaceful assembly and freedom of expression are fundamental human rights and fall within Libya's obligations under international human rights law," the statement said.

The demonstrations in the country are motivated by deep-seated frustrations about sustained poor living conditions, shortages of electricity and water, rampant corruption, misgovernance, and a lack of service provision throughout the country, the mission said.

The demonstrations underscore the urgent need to lift the oil blockade and return to a full and inclusive political process that will meet the aspirations of the Libyan people for representative government, dignity, and peace, the mission said.

Protests broke out in a number of cities in eastern Libya against lack of basic services, mainly electricity, healthcare and funds in local banks.

The eastern-based government of Libya, headed by Abdullah Al-Thani, on Sunday presented its resignation to the eastern-based House of Representatives (parliament) following three days of protests in eastern Libya.